Amplifiers come in many forms and are used in many applications. For example, amplifiers may be used with digital or analog signals in communications systems such as, for example, wireless telecommunications and satellite communications systems. Generally, amplifiers are either semiconductor-based or vacuum tube-based. Because electrons can travel at a higher velocity in a vacuum than in a semiconductor, vacuum tube amplifiers may be fabricated from structures that are larger relative to those of semiconductor-based devices but that have comparable transit times. Larger structures permit greater power levels. Accordingly, vacuum tube microwave power amplifiers, such as traveling wave tube (TWT) amplifiers, are used as power amplifiers in modern microwave systems, including telecommunications, radar, electronic warfare, and navigation systems, due to their ability to provide microwave energy at power levels orders magnitude higher than those of semiconductor microwave amplifiers.
Conventional vacuum tube microwave power amplifiers that utilize cylindrical electron beam geometries may not be suitable for high frequency and high bandwidth applications. In particular, electron beam diameter in such devices may be scaled with radio-frequency (RF) wavelength, while electrical current may be scaled with RF power. Therefore, at higher frequency and power, current density may exceed the confinement capability of known magnetic materials, which, in turn, limits amplifier power and bandwidth.
One advantage of electron sheet beam-based amplifiers is that beam thickness and width are scaled differently with frequency, thereby enabling higher current with lower current density to be transported in a smaller sized tube. Conventional wide band slow wave structures (SWS) (e.g., a helix SWS) for amplifying RF waves are not suitable for electron sheet beam configurations.